Various small-size containers are in use to contain liquid medicines, such as eye drops, and to discharge medicines therefrom, drop by drop, by squeezing the body of the container with fingers. The body resiliently restores its original shape as soon as the pressure is released after the discharge. At that time, the container faces a problem as outside air creeps in the container along with airborne foreign matters and bacteria, which may contaminate the liquid content.
As the means of solving this problem, Japanese patent applications P1992-297264 and P1994-14972 describe a method of adding a filter inside the content discharge path. Utility model laid open No. 1988-183047 describes a method of putting restraints on the entry of outside air by giving a flat shape to the end of the container or by making the body flat and foldable so that the volume of the container will be decreased with the decrease in the content.
As another method of preventing outside air from coming in the inside of the container, utility model laid open No. 1995-22951 describes a double-layered container. A discharge cap is put to cover the opening of the container (outer container) in which to place the inner container. This cap is provided with a content discharge valve, which is able to discharge the content but does not take in outside air, and with an air suction valve, which is able to take in outside air but does not discharge air outside. Because of the action of these valves, air is introduced into the void between the inner and outer containers with the decrease in the content.
However, the method of adding a filter inside the content discharge path has problems of filter clogging or bacterial growth in the filter. The method of flattening the end of the container according to utility model laid open No. 1988-183047 is mainly an application of toothpaste tubes, and had a problem of inconvenience in use and a problem of outer appearance.
The double-layered container according to utility model laid open No. 1995-22951 has a complicated configuration. Especially, the discharge cap not only connects and fixes the outer and inner containers to each other, but also is provided with the function of an air intake valve, which is able to take in outside air and would not allow air to escape outside. In the case of small-size discharge containers such as eyedroppers, it is difficult, and not feasible in reality, for the container to have such a function while maintaining high productivity.
This invention has been made to solve the technical problems found in conventional art. The technical problem of this invention is to create feasible check valve mechanisms for use in small-size double-layered containers, while maintaining high productivity. The object of this invention is to provide a highly sanitary discharge container of a double-layered structure having high productivity and no entry of outside air into the inner container.